(a) Field of the Invention:
The present invention relates to a video endoscope system provided with color balance adjusting means.
(b) Description of the Prior Art:
In conventional video endoscope system, as shown in FIG. 1, a video system forming a color picture image has comprised an electronic endoscope 1 including an image pickup device, a light source device 2 supplying light to an illumination system of the electronic endoscope 1, a video signal processing circuit 3 including a color balance adjusting circuit which receives an output signal issued from the image pickup device of the electronic endoscope 1, thereby forming a video signal, and a TV monitor 4 receiving the signal of the video signal processing circuit 3 to make video display. However, each of the components of this system has irregularity in manufacture, so that the color of the color picture image displayed finally on the TV monitor 4 frequently varies, which has prevented exact diagnosis from being made for a patient. Further, in addition to the TV monitor 4, a TV picture image photographing device 5 is connected to the system mentioned above, and is constructed so that the picture image displayed on a TV monitor 6 for exclusive photographing, housed in the device 5, is photographed on a film 8 through a lens 7. Also in such a case, however, the color of the color picture image displayed on the TV monitor varies with considerable frequency, with the result that difficulties have been encountered that a recorded photograph shows different colors and exact diagnosis is likewise prevented.
Thus, in the video endoscope system, like a common video camera for home use, it has been devised that a white board is placed in front of the electronic endoscope 1, as shown in FIG. 2, to adjust color balance. Since, however, illuminance of illumination light emitted onto the white board from the endoscope is uneven with respect to an illumination angle .theta. as graphed in FIG. 3, the picture image displayed on the TV monitor through the video signal processing circuit 3 is bright in its center and dark in its circumference, with the variation of tone as well as brightness, and consequently the adjustment of the color balance with a high degree of accuracy has been difficult.